In a package body comprised of a laminate plastic film for package filling and packing a liquid material, there is a fear that if ambient air (air), dust and so on are enclosed together with a liquid packed material into the package body, the liquid packed material is oxidized in the bag to deteriorate taste of the liquid packed material or fungi might grow in the bag. Therefore, as a method for filling the liquid packed material into the package bag without allowing invasion of air or the like are used a method of replacing air in the bag with nitrogen after the filling of the liquid packed material (Patent Document 1) and a sealing method wherein the liquid packed material is fully filled in the package bag and then subjected to a lateral sealing at this state while pushing the extra packed material with a lateral sealing roller (hereinafter referred to as “in-liquid seal packing”, Patent Document 2).
In the method disclosed in the Patent Document 1, however, when nitrogen gas is injected into the package bag, there is a high possibility that air and dusts are caught in the package bag or the liquid packed material due to the injection and remain therein as they are, and hence it is impossible to encapsulate only the desired gas into the package bag. Therefore, this method has problems that facilities become large-scale for making an atmosphere in a whole of a room placing a filling-packing machine into a nitrogen gas atmosphere or the like and the amount of the gas used becomes large and the cost becomes higher.
In the method disclosed in the Patent Document 2, it is possible to fill the liquid packed material without allowing invasion of air or the like, but there is a fear that if it is intended to fill, for example, nitrogen gas, carbon dioxide gas or the like together with the liquid packed material, such a gas rises to an upper part of the liquid packed material and hence the necessary amounts of the gas and the liquid packed material cannot be filled exactly in the package bag. According to this method, the gas is easily caught in a seal portion and expanded by heating with a heat seal roller to form big bubbles to thereby cause blisters, and hence it is feared to cause the breakage of the seal portion, the leakage of the packed material and so on.
In recent years are proposed package bags provided with a pouring nozzle having a one-way function in which invasion of air or the like into the package bag not only in the filling of the liquid packed material but also after the opening of the package bag and hence oxidation, pollution or the like of the liquid packed material is suppressed over a long duration (Patent Documents 3 and 4).
In such a package bag, since the pouring port has the one-way function, ambient air is never taken into the package bag even if the liquid packed material is poured repeatedly. Accordingly, the package bag main body is shrunk and deformed associated with the pouring of the liquid packed material at only a volume corresponding to the amount of the packed material poured. In such a package bag, therefore, when the remaining amount of the liquid packed material in the package bag is large, laminate films for packing in the package bag main body are separated sufficiently widely in front and rear directions under an action of a big water head pressure of the liquid packed material by tilting the package bag body to open a pouring path relatively quickly, whereby the liquid packed material can be poured smoothly through the opened tip of the pouring nozzle. However, when the remaining amount of the liquid packed material is decreased to not more than about ⅓ of the initial amount in such a package bag, the front and rear laminate films for packing are adhered tightly to each other associated with the shrinkage or deformation of the package bag main body and hence the free flow of the liquid packed material is inhibited in the package bag. Furthermore, in case of filling a liquid packed material such as a dressing, which is necessary to be squeezed initially in use, it is required to squeeze out the package body itself, and hence quick pouring becomes impossible. In this method, therefore, a time lag to the pouring of the liquid packed material through the opened tip of the pouring nozzle becomes large and it is difficult to pour the full remaining amount of the liquid packed material in the shrunk package bag.
As a method for relieving the adhesion force between the front and rear laminate plastic films in the package bag main body, it is preferable to encapsulate an inert gas not affecting the liquid packed material such as nitrogen gas, argon gas and so on or other gas together with the liquid packed material into the package bag. In the methods disclosed in Patent Documents 1 and 2, however, it is difficult to fill both of the required amount of the liquid packed material and the gas into the package bag without allowing invasion of ambient air.